1. Field of the Disclosure
This disclosure generally relates to an optical physiological detection system and, more particularly, to a physiological detection system with adjustable signal source and an operating method thereof.
2. Description of the Related Art
Conventional pulse oximeters utilize a noninvasive method to monitor the blood oxygenation and the heart rate of a user. The conventional pulse oximeters generally emit a red light beam (wavelength of about 660 nm) and an infrared light beam (wavelength of about 910 nm) to penetrate a part of the human body and detect an intensity variation of penetrating light based on that the oxyhemoglobin and the deoxyhemoglobin have different absorptivities in particular spectrum. After the intensity variation of the penetrating light, e.g. photoplethysmography signal or so called PPG signal, of the two wavelengths is detected, the blood oxygenation can then be calculated according to the following equation:Oxygen saturation=100%×[HbO2]/([HbO2]+[Hb])
wherein [HbO2] is oxyhemoglobin concentration; and [Hb] is deoxyhemoglobin concentration.
Generally, the intensity variation of the penetrating light of the two wavelengths detected by a pulse oximeter becomes strong and weak with the heartbeat. This is because blood vessels will expand and contract with the heartbeat such that the blood volume that the light beams pass through will change to accordingly change the ratio of light energy being absorbed. Accordingly, it is able to calculate a physiological characteristic of the user according to the detected PPG signal(s).
However, when an optical physiological detection device is applied to a portable device or a wearable device, a detection surface thereof can have a relative movement with respect to a skin surface or the detection surface is not tightly attached to the skin surface such that the signal quality of detected signals is reduced to degrade the detection accuracy.